linux-kernel - RE: [PATCH iwl-next v2 4/8] ice: allow overriding lan_en, lb

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Message-ID: <IA3PR11MB8986430837663B174A8AFDA9E5DBA@IA3PR11MB8986.namprd11.prod.outlook.com>
Date: Mon, 1 Dec 2025 07:37:02 +0000
From: "Loktionov, Aleksandr" <aleksandr.loktionov@...el.com>
To: "Slepecki, Jakub" <jakub.slepecki@...el.com>,
	"intel-wired-lan@...ts.osuosl.org" <intel-wired-lan@...ts.osuosl.org>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>, "Kitszel, Przemyslaw"
	<przemyslaw.kitszel@...el.com>, "Nguyen, Anthony L"
	<anthony.l.nguyen@...el.com>, "michal.swiatkowski@...ux.intel.com"
	<michal.swiatkowski@...ux.intel.com>
Subject: RE: [PATCH iwl-next v2 4/8] ice: allow overriding lan_en, lb_en in
 switch



> -----Original Message-----
> From: Slepecki, Jakub <jakub.slepecki@...el.com>
> Sent: Friday, November 28, 2025 12:56 PM
> To: Loktionov, Aleksandr <aleksandr.loktionov@...el.com>; intel-wired-
> lan@...ts.osuosl.org
> Cc: linux-kernel@...r.kernel.org; netdev@...r.kernel.org; Kitszel,
> Przemyslaw <przemyslaw.kitszel@...el.com>; Nguyen, Anthony L
> <anthony.l.nguyen@...el.com>; michal.swiatkowski@...ux.intel.com
> Subject: Re: [PATCH iwl-next v2 4/8] ice: allow overriding lan_en,
> lb_en in switch
> 
> On 2025-11-25 9:59, Loktionov, Aleksandr wrote:
> >>   	if (fi->flag & ICE_FLTR_TX_ONLY)
> >> -		fi->lan_en = false;
> >> +		lan_en = false;
> >> +	if (!FIELD_GET(ICE_FLTR_INFO_LB_LAN_FORCE_M, fi->lb_en))
> >> +		FIELD_MODIFY(ICE_FLTR_INFO_LB_LAN_VALUE_M, &fi->lb_en,
> lb_en);
> >> +	if (!FIELD_GET(ICE_FLTR_INFO_LB_LAN_FORCE_M, fi->lan_en))
> >> +		FIELD_MODIFY(ICE_FLTR_INFO_LB_LAN_VALUE_M, &fi->lan_en,
> lan_en);
> > fi->lb_en and fi->lan_en are declared as bool in struct
> ice_fltr_info,
> > but you are now treating them as bitfields using FIELD_GET and
> > FIELD_MODIFY.
> 
> I don't see what you mean here.  Both members are u8 without a bit-
> field declaration.  Or do you mean they are used as bool or maybe the
> _en suffix?
> 
> > I realize it could be something like:
> > struct ice_fltr_info {
> >      ...
> >      u8 lb_lan_flags; /* bitfield: value + force */
> >      ...
> > };
> 
> What I see from this sample is that you want me to: pack them, change
> their name, and change their description.  Is this correct?
> 
> I fully agree about the description.  It's my mistake I left it as-is.
> I'll update it according to the overall changes.
> 
> I don't think packing them is worth it.  The memory gain is negligible
> and the cost is primarily in readability and consistency: we've always
> had two fields for these with clear responsibility for each, names
> match with datasheet (both "lan en" and "lb en" will hit Table 7-12.),
> and packing them would require twice as many constants.
> 
> Would the clarification in the description be enough to address your
> concerns?  Something like (please ignore bad line breaks):
> 
> struct ice_fltr_info {
> 	...
> 	/* Rule creation will populate VALUE bit of these members based
> on switch
> 	 * type if their FORCE bit is not set.
> 	 */
> 	u8 lb_en;	/* VALUE bit: packet can be looped back */
> 	u8 lan_en;	/* VALUE bit: packet can be forwarded to uplink
> */
> };
> 
> > #define ICE_FLTR_INFO_LB_LAN_VALUE_M    BIT(0)
> > #define ICE_FLTR_INFO_LB_LAN_FORCE_M    BIT(1)
> > #define ICE_FLTR_INFO_LB_LAN_FORCE_ENABLED \
> >      (FIELD_PREP_CONST(ICE_FLTR_INFO_LB_LAN_VALUE_M, 1) | \
> >       FIELD_PREP_CONST(ICE_FLTR_INFO_LB_LAN_FORCE_M, 1)) #define
> > ICE_FLTR_INFO_LB_LAN_FORCE_DISABLED \
> >      (FIELD_PREP_CONST(ICE_FLTR_INFO_LB_LAN_FORCE_M, 1))
> 
> Does this mean you want me to use {1,0} instead of {true,false}?
> 
> In ice_fill_sw_info() I'd prefer to keep them as boolean because they
> are semantically correct: we're calculating defaults and then we apply
> them if specific values are not forced elsewhere.  Maybe a comment or
> docs change would be more in place?  In
> ICE_FLTR_INFO_LB_LAN_FORCE_{ENABLED,DISABLED},
> I used boolean to stay consistent with the ice_fill_sw_info().
> 
> But it's not a strong preference.  If it's preferable, I'll change it
> to {1,0} across the patch.
> 
> Thanks!

For u8 fields if they are used as u8 value (not bit fields) using FIELD_ macros not good.
What about compromise:
 - Keep lan_en and lb_en as bool or u8 with clear comments.
 - Do NOT use FIELD macros unless these fields are truly packed bitfields.
 - If FORCE/ VALUE semantics are needed, either:
   +Introduce a dedicated flags field with proper bitmask macros, OR
   +Keep separate fields and handle FORCE logic explicitly in code without FIELD macros.

And handle FORCE logic explicitly:

if (!force_lb)
    fi->lb_en = lb_en;
if (!force_lan)
    fi->lan_en = lan_en;

?